I. Field of the Invention
The present invention pertains generally to refuse collection vehicles and to associated material handling equipment including a vehicle body having a collection receiving receptacle and an integral container lifting and tipping mechanism for use during collection efforts. More particularly, the invention focuses on loading mechanisms for front loading refuse trucks and on an aspect related to the control and stowage for travel of the lift forks of a container lifting and tipping apparatus characterized by pivoting lift arms and connected lift forks.
II. Related Art
Front loading-type refuse handling equipment typically includes a pair of spaced lift arms connected to opposite sides of the vehicle body and a pair of extendable lift forks connected to pivot from joints at the ends of the lift arms and designed to engage corresponding fork receiving passages or recesses connected to the opposite sides of a refuse container for lifting and dumping the refuse container into a refuse charging hopper on the vehicle.
The arms and forks are designed to pivot in parallel planes in the direction of the vehicle length to address a container in front of the vehicle and lift it over the cab and empty the container into a charging hopper behind the cab. The forks are designed to be rotated forward as a container is lifted by a rearward pivoting action of the spaced arms to maintain the container in a generally upright position until it is over the charging hopper where the forks are rotated rearward to tip the container.
With regard to the design of the mechanism for lifting and tipping containers, when the system is in use, it is necessary to limit the rearward pivotal travel of the forks relative to the lift arms to prevent the container from contacting the ejector or other internal parts in the charging hopper which might cause the container to be lifted off the forks and allowed to fall into the hopper or otherwise damage either the container or the vehicle. When the front loader is traveling down the road, other factors come into play. It is clearly undesirable for the lift arms to be in their fully lowered position with the forks protruding horizontally, this extends the overall length of the vehicle and leaves the protruding forks in a position where they can easily cause damage to objects or be damaged themselves. On the other hand, if the arms are allowed to remain in the fully raised position, the forks protrude upward and the vehicle may exceed legal height limitations or the allowable useful storage height must be reduced accordingly.
It has, therefore, become customary to drive such front-loading vehicles with the arms and forks in a partially raised position to avoid these problems. This solution, however, also creates problems of its own. In the partially raised position, the forks are located at a height approximately equal to the top of the windshield on the truck cab which can distract the driver. It has also been found that this may produce undesirable sway during movement of the vehicle; and driving with the arms in the partially raised position transmits additional road shock and impact to the arm pivot bearings located on the body of the vehicle which produces rapid wear and early failure. It appears that travel with the fully raised arms potentially provides the fewest problems. Thus, it would be desirable if the vehicle could travel over the road with the arms in the fully raised position if the over height problem could be resolved.
One alternate solution to the situation is presented in U.S. Pat. No. 4,547,118 to Pittenger in which the pivotal fork arms are made foldable vertically relative to the lift arms when the latter are in a lowered or transport position to eliminate horizontal protrusion. That mechanism also includes a cam abutment arrangement to establish the minimum angle to which the fork arms can be moved relative to the lift arms in the container unloading position to prevent interference between the vehicle and the refuse container.
It would desirable, however, to provide a mechanically uncomplicated system that limits fork travel to permit safe tipping yet allows the forks to be fully retracted into the charging hopper when the arms are in the fully raised position for travel down the road. In this manner, there would be two required positions for the forks when the arms are fully raised; namely, one position for tipping a container into the receiving or charging hopper and one fully folded position for traveling which exceeds the tipping or working position. Attempts have been made to accomplish this, for example, by sensing the position of the forks with a proximity or mechanical switch which can be used to limit the travel depending on whether a working or traveling mode is desired. A system of this nature, unfortunately, involves wiring, wire routing, switches and the like which produce, in the end, a complex system which may fail and leave the loading mechanism totally inoperative.
There clearly remains a need to provide an uncomplicated method for controlling the position of the forks so that both a working position and a traveling position can be realized without additional moving parts or complicated electrical or electromechanical interlocks.
Accordingly, it is a primary object of the present invention to provide an improved control system for a lifting and tipping apparatus associated with a front loading refuse vehicle having pivoting lift arms and lift forks which improves the flexibility of operation of the lift forks.
A further object of the present invention is to provide an improved control system for operating the rotating lift forks associated with a front loading refuse vehicle which allows the forks to have one folded position for container tipping and one for stowage.
Another object of the present invention is to provide an improved control system for a lifting and tipping apparatus associated with a front loading refuse vehicle which allows stowage of the forks for travel with the lift arms in their fully elevated position.
A still further object of the present invention is to provide an improved control system for a lifting and tipping apparatus associated with a front loading refuse vehicle which allows multiple folding positions of the lift forks and yet does not interfere with the normal lifting and tipping cycle.
A yet still further object of the present invention is to provide an improved control system for a lifting and tipping apparatus associated with a front loading refuse vehicle which controls the rotation of the lift forks by controlling the operating speed of the lift fork cylinders.
Yet another object of the invention is to provide a flow-limiting, speed-modulating or cushioning system with respect to the operation of the lift fork cylinders of a lifting and tipping apparatus associated with a front loading refuse vehicle.
Other objects and advantages will occur to those skilled in the art upon familiarization with the specification and drawings contained herein.